You probably noticed a wide variety of answers. It really comes down to what you like. If you observe a 8x10 picture in a simple 8x10 frame it has more of a snap shot look. An 8x10 print with a nice mat in an 11x14 frame or even a 16x20 frame will have significantly more presence. For a larger image, an alternative is float mounting it in a frame that is just a little larger, say 23x31, but deeper like a shadow box frame. The later requires what is typically a custom spacer though. If you want the frame to protect the image over time you do not want it against the glass so you will need a mat or spacer. The clasic gallery style photo framing consists of a simple black frame with a white mat. For an image that size I would suggest you go with at least 3 inches but 4 or 5 inches as shown in ROL's example photo will give it more of a gallery feel. Of course, larger mat means larger frame, glass and backing so more money.